to install an extension, just extract the 7z compressed file inot the k-meleon folder. the performancing extension needs some intervention from the user the first time its installed so it can work properly. you will need to register the component files..this is easily done by going to k-meleon\components folder and deleting those 2 files:
xpti.dat
compreg.dat

those files will be recreated when you restart kmeleon and will register the performancing service files

another thing you will have to do is add a couple of files called wizard files to k-meleon embed and locale chrome jars..it's fairly easy to add them and the performancing package includes a readme file on how to add them to kmeleon chromes.

if you are using the english version of k-meleon, you can just download those 2 modified chrome files with the wizard files included:
http://kmext.sourceforge.net/chromes
save them to k=meleon\chrome folder (replace the existing embed.jar and en-us.jar)